GB2091841A - Valved shock absorber piston - Google Patents

Abstract

A hydraulic shock absorber for a motor cycle comprises a cylinder 1 for containing hydraulic fluid, a hollow piston 4 slidable in the cylinder, and a check valve assembly 2 arranged in the piston and operable to allow hydraulic fluid to pass from one side of the piston to the opposite side upon relative movement of the piston in the cylinder. The check valve assembly comprises a valve body 2b and a valve seat 2c, first ports 2e extending through the valve body to communicate with both sides of the piston, and second ports 7 which also serve to provide communication between the opposite sides of the piston, the second ports 7 opening at one end at the valve seat. A valve element 2d controls the flow of fluid through the ports 2e. The inner surface of the hollow piston 4 forms a valve casing which surrounds the valve assembly, and the second ports 7 are formed in this inner surface in the form of semi-cylindrical recesses which are closed-off by the outer surface of the valve body 2b. This removes the head for a separate valve casing. <IMAGE>

Description

SPECIFICATION Hydraulic damper This invention relates to a hydraulic damper or shock absorber which is suitable for use in a vehicle, such as a motorcycle or the like.

One known construction of hydraulic damper or shock absorber is shown in Figure 1 of the accompanying drawings. the damper comprises a cylinder a which contains an hydraulic fluid, a piston c which is slidable in the cylinder, and a check valve assem blyb mounted within the piston c. The check valve assembly b comprises a valve seat h which is retained in position at one end of the piston c, a valve body g, and a compression spring fwhich reacts between a surrounding valve casing e and the valve bodyg in order to urge the latter towards the valve seat h.

As will be seen in Figure 1, axially extending ports are formed in the valve body g which are open at their upper ends, and which are closed at their lower ends by an annular valve element which is positioned between the lower end of the valve body g and the upper end of the valve seat h. When the piston c moves upwardly, the hydraulic fluid in the cylinder a above the piston can flow in a reverse direction i.e. downwardly through the ports, since the valve element is displaced so as to open the lower ends of the ports. When the piston c moves downwardly, the valve element seals the entrances to the ports in the valve body g, but axially extending ports dare then allowed to provide direct communication between the opposite sides of the piston c so that hydraulic fluid can pass from the lower side of the piston cto the upper side.Thus, during downward movement of the piston c, the valve element is pressed upwardly against the valve body g, which moves upwardly against the action of the spring fin order to unblock communication with the lower end of the ports dadjacentto the valve seat h.

As will be seen in Figure 1, the ports dare formed between the inner surface of the valve casing e and the outer surface of the valve body g.

The present invention has been developed primarily, though not exclusively, with a view to improving the construction of hydraulic damper, as shown in Figure 1,so as to simplify its construction, and reduce its weight.

According to the invention there is provided a hydraulic damper comprising a cylinder for containing hydraulic fluid; a hollow piston slidably mounted in said cylinder for movement in relatively opposite first and second directions relative to the cylinder; a check valve assembly arranged in said piston and operable to allow hydraulic fluid to pass from one side of the piston to the opposite side of the piston upon relative movement of the piston in the cylinder; a valve body and a valve seat provided in said check valve assembly; a first port extending through the valve body to communicate with said one side and with said opposite side of the piston; a valve element arranged between the valve body and the valve seat and operable to control the flow of hydraulic fluid through the port, the valve element preventing flow through the port when the piston carries out relative movement in said first direction and allowing fluid flow through the port in said first direction when the piston carries out relative movement in said second direction; and a second port which is communicable with both sides of the piston and which opens at one end at said valve seat, the valve element also controlling said second port so as to allow fluid flow through the second port in second direction when the piston moves relatively in said first direction, and to prevent fluid flow through the second port when the piston moves relatively in said second direction and the valve element becomes seated against the valve seat so as to block communication with said one end of the second port; in which the inner surface of the hollow piston forms a valve casing which surrounds said valve assembly, and said second port is formed in said inner surface.

One embodiment of hydraulic damper according to the invention will now be described in detail, by way of example only, with reference to Figures 2 to 4 of the accompanying drawings in which Figure 2 illustrates the operation of the hydraulic damper when the piston moves downwardly relative to the cylinder of the damper; Figure 3 illustrates the operation of the hydraulic damper when the piston moves upwardly relative to the cylinder; and Figure 4 is a horizontal cross sectional view of the hydraulic damper.

Referring now to Figures 2 to 4 of the drawings, the hydraulic damper which is illustrated is particularly suitable for use in a vehicle, or a motorcycle.

The hydraulic damper comprises a cylinder 1 for containing hydraulic fluid, a piston 4 slidably mounted in the cylinder 1 for movement relative thereto, a check valve assembly 2 arranged in the piston 4 (which is hollow) and a piston rod 3 which extends upwardly from the piston 4. The piston 4 is manufactured in any convenient manner, and preferably by press working into a cylindrical shape which is open downwardly. At the lower end of the piston 4, there is a flange 6 which is bent radially inwardly in order to retain the check valve assembly 2 within the piston 4. The piston rod 3 is connected, by welding or any other convenient manner, to the upper portion of the piston 4 so as to extend upwardly therefrom.

The check valve assembly 2 comprises a compression spring 2a, a valve body 2b positioned below the spring 2a, and a valve seat 2c which is located below the valve body 2b and which is retained in position by the annular flange 6. The valve body 2b is biased downwardly towards the valve seat 2c by means of the spring 2a.

First ports 2e extend through the valve body 2b and communicate freely at their upper ends with the hydraulic fluid in the cylinder 1 above the piston 4, but the opening and closing of their lower ends is controlled by means of an annular valve element in the form of a reed valve 2d. When the piston rod 3 moves downardly in the direction of the arrow shown in Figure 2, the reed valve 2d is pressed upwardly into firm sealing engagement over the lower ends of the first ports 2e, so as to prevent fluid flow in an opposite direction through the ports 2e.

Second ports 7 are also provided in the check valve assembly 2, which serve to convey hydraulic fluid from below the piston 4, to above the piston 4, when the entrances to the ports 2e are blocked by the reed valve 2d. It will be noted that the upper ends of the second ports 7 have free communication with the hydraulic fluid in the cylinder 1 above the piston 4, but the lower ends of the second ports 7 open at the upper seating surface of the valve seat 2c.

Although the valve body 2b and the reed valve 2d are normally biased downwardly by the spring 2a into seating engagement with the valve seat 2c (so as to block communication to the lower ends of the ports 7), downward movement of the piston rod 3 (a first direction) causes the valve body 2b and the valve reed 2d to move upwardly against the action of spring 2a so as, in addition to blocking entrance to the first ports 2e, to unblock the entrance to the lower ends of the second port7. Hydraulic fluid can then flow upwardly through the second ports 7 (in a second direction) which is opposite to the direction of relative movement of the piston 4 in the cylinder 1.

As will be seen from Figures 2 to 4, and particularly Figure 4, the second ports 7 are axially extending ports which are actually formed in the inner surface of the hollow piston 4. The ports 7 comprise semi-cylindrical recesses formed in the cylindrical inner wall of the hollow piston 4, and are equally circumferentially spaced from each other along the inner wall. Each semi-cylindrical recess is closed-off by the cylindrical outer surface of the valve body 2b.

Thus, instead of the provision of a separate valve casing, such as the valve casing e shown in Figure 1, the hollow piston 4 itself forms the outer valve casing for the check valve assembly 2. The parts 2a, 2b, and 2c of the check valve assembly 2 are directly incorporated within the hollow piston 4, so that the piston 4 can serve, in addition to acting as a piston, as the surrounding valve casing for the check valve assembly.

The piston 4 is provided with a piston sealing arrangement 8 which comprises an upper ring 8a and a lower ring 8b.

As mentioned above, Figure 2 illustrates the mode of operation of the hydraulic damper when the piston 4 carries out downward movement relative to the cylinder 1. However, Figure 3 illustrates the mode of operation of the damper when the piston 4 carries out upward movement relative to the cylinder 1. Thus, when the piston 4 moves upwardly, the valve body 2b is urged downwardly, in addition to the biasing provided by the spring 2a, so as firmly to trap the outer periphery of the reed valve 2d between the upper seating surface of valve seat 2c and the radially outer peripheral, and lower, edge of the valve body 2b. This causes communication with the lower ends of the second ports 7 to be blocked.

However, the upward movement to the piston 4 causes hydraulic pressure to be exerted in a downward direction on the reed valve 2d, which therefore opens, as shown in Figure 3, in order to uncoverthe lower ends of the first ports 2e. This allows hydraulic fluid to pass in a downward direction (the first direction) through the first ports 2e from above the piston 4to below the piston 4.

According, the construction of hydraulic damper according to the embodiment of the invention, as shown in Figures 2 to 4, can function in similar manner to the dampr shown in Figure 1, but has the advantage of a simplified, and also lighter weight construction. This is by virtue of the fact that the piston 4 is provided in its inner circumferential surface with a number of axially extending hydraulic grooves or ports so that the piston acts as a valve casing surrounding a check valve assembly, whereby the number of the constructional components is decreased. This provides a simpler construction, which is smaller in weight that the previously proposed construction wherein a separate valve casing is provided.

Claims (9)

1. A hydraulic damper comprising a cylinderfor containing hydraulic fluid; a hollow piston slidably mounted in said cylinder for movement in relatively opposite first and second directions, relative to the cylinder; a check valve assembly arranged in said piston and operable to allow hydraulic fluid to pass from one side of the piston to the opposite side of the piston upon relative movement of the piston in the cylinder; a valve body and a valve seat provided in said check valve assembly; a first port extending through the valve body to communicate with said one side and with said opposite side of the piston; a valve element arranged between the valve body and the valve seat and operable to control the flow of hydraulic fluid through the port, the valve element preventing flow through the port when the piston carries out relative movement in said first direction and allowing fluid flow through the port in said first direction when the piston carries out relative movement in said second direction; and a second port which is communicable with both sides of the piston and which opens at one end at said valve seat, the valve element also controlling said second port so as to allow fluid flow through the second port in second direction when the piston moves relatively in said first direction, and to prevent fluid flow through the second port when the piston moves relatively in said second direction and the valve element becomes seated against the valve seat so as to block communication with said one end of the second port; in which the inner surface of the hollow piston forms a valve casing which surrounds said valve assembly, and said second port is formed in said inner surface.

2. A hydraulic damper according to claim 1, including a plurality of said first and second ports.

3. A hydraulic damper according to claim 1 or 2, in which the or each second port extends parallel to the longitudinal axis of the cylinder.

4. A hydraulic damper according to any one of the preceding claims, in which the or each second port comprises a semi-cylindrical recess formed in the inner surface of the hollow piston, the or each recess being closed by the outer surface of the valve body.

5. A hydraulic damper according to claim 4, including a plurality of semi-cylindrical recesses circumferentially spaced from each other by equal distances.

6. A hydraulic damper according to any one of the preceding claims, in which the valve seat is mounted in position at one end of the piston by means of a flange at said one end of the piston which is bent radially inwardly in order to retain the valve seat.

7. A hydraulic damper according to claim 6, in which the valve body is spring biased from the opposite end of the piston towards the valve seat.

8. A hydraulic damper according to claim 1 and substantially as hereinbefore described with reference to, and as shown in Figures 2 to 4 of the accompanying drawings.

9. A hydraulic shock absorber or damper for a vehicle, or motor cycle, comprising a hydraulic damper according to any one of the preceding claims.